You can treat the foreground independently from the trails. Take a foreground shot exposed for the foreground, and you can blend it with the trails after. While I haven't tried it myself, you can also try light painting using a torch and long exposure. Obviously depends on the size of the foreground subject.

I've seen mentioned many times that for stacking, don't folk take a black/blank image (cap on the lens?) to keep the night sky dark when they stack images, or is it just relevant to you astro/deep sky guys?